The student-loan-debt crisis is massive. Americans owe more than $1 trillion in student loans, and according to a July report by the Consumer Financial Protection Bureau, $150 billion of these student loans are from private lenders, which means they often come with higher interest rates than federal loans and are almost impossible to shed in bankruptcy proceedings.

Nightmare stories about young adults struggling under mountains of student-loan debt appear in the media nearly every day. But how many college students are using their loans only for necessities? How many are taking out more money than they need and blowing it on silly stuff that they’ll be paying off for years or even decades to come?

I conducted some informal research to determine how endemic the misuse of loans really is. I tapped my kids as well as other recent college graduates, friends and co-workers, and I was stunned at how pervasive this seems. When I asked my stepson, who graduated last winter, if he knew of kids using their student loans for non-school-related purchases, his response was, “Don’t even get me started.”

First, he told me about a family friend who, a few months ago when she was a junior in college, used her student-loan money to buy a used car. I almost flipped. Didn’t she realize this means she’ll be paying that car off — at an interest rate almost twice as high as a typical auto loan — long after it breaks down?

My colleague Meghan, also a recent grad, mentioned classmates who had purchased flat-screen TVs, sound systems and trendy decor for their dorm rooms. I heard from various people about kids using student loans to pay for expensive spring-break trips, clothes and, a common refrain, “partying.” These students will be paying high interest rates for purchases they probably won’t even remember in five years.

So listen up, parents: this fall, as funds from student loans make their way into college students’ bank accounts, it is critical that your child understands how loans work. For many young adults, cash just seems like cash — regardless of how they got it. But not all money is created equal, and not all loans are equal either. For example, if our family friend had taken out an auto loan to fund her used car, she likely would have paid interest closer to 3.5% than the 6.8% on the federal government’s direct unsubsidized loans, which are available to undergraduates and grad students and don’t require them to demonstrate financial need. Going the auto-loan route would have meant the length of the loan would have been more appropriate too.

Using student loans like a credit card can be very costly to young adults — and to the parents who co-sign these loans. In many cases, interest on private loans starts accruing even while the student is still in school. Repayment periods for these loans can extend for long periods — sometimes 20 to 30 years following graduation — which may make the monthly repayments seem less onerous on the surface, but the interest can really rack up over time. Having a conversation now with your child is important before he or she unintentionally creates a financial mess down the road.

As parents, we have to accept that our kids will make mistakes — it’s our job to help mitigate them. Work closely with your child to ensure that he or she is borrowing only what’s needed and talk regularly about how the funds are being used. And to help minimize debt, tell your kid to follow this sage advice from FinAid.org: “Live like a student while you are in school so you don’t have to live like a student after you graduate.”